The present invention relates to methods for controlling the migration of unconsolidated particulates in a subterranean formation. More particularly, the present invention relates to the use of treatment fluids comprising relatively dilute resin compositions for controlling the migration of unconsolidated or weakly consolidated particulates in a portion of a subterranean formation wherein the relatively dilute resin compositions comprise an aqueous dissolvable solvent.
Hydrocarbon wells are often located in subterranean formations that comprise unconsolidated portions, that is, portions of a subterranean formation that contain particulate matter capable of migrating out of the formation with produced fluids. Unconsolidated portions of subterranean formations include those that contain loose particulates that are readily entrained by produced fluids and those wherein the particulates are bonded together with insufficient bond strength to withstand the forces produced by the production of fluids through the zones. The presence of particulate matter, such as sand, in produced fluids may be disadvantageous and undesirable in that such particulates may abrade pumping equipment and other producing equipment and may reduce the fluid production capabilities of the producing portions of the subterranean formation.
One method of controlling unconsolidated particulates involves placing a filtration bed of gravel near the well bore to prevent the transport of unconsolidated formation particulates with produced fluids. Typically, such operations are referred to as “gravel packing operations,” and they usually involve pumping and placing a quantity of particulates adjacent to a portion of an unconsolidated formation so as to form a gravel pack between the open well bore and the formation walls. Although used frequently, such methods can be time-consuming and expensive to perform.
Another conventional method used to control loose formation particulates in unconsolidated formations involves consolidating a portion of a subterranean formation from which the unconsolidated particulates tend to flow by applying a curable resin composition to that portion. In one example of such a technique, an operator pre-flushes the formation, applies a resin composition, and then applies an after-flush fluid to remove excess resin from the pore spaces within the formation. Such resin consolidation methods, however, have not been practicable on formations containing reactive mineral clays such as smectite and kaolinite. Resin consolidating treatments performed on such reactive clay-laden formations tend to yield little or no improvement in consolidation strength and/or may cause significant loss of permeability.